Consistent with a dare, like saying I dare you to do something. If a "No Balls" is refused, the refuser therefore has no balls and may be reminded of this constantly; The highest form of a dare to ever exist.

Cheyenne: "Courtney, no balls you won't chug this 12 pack in under an hour!"

A dare; to challenge to do something requiring boldness and a slight lack of common sense, quite often ending in pain, discomfort, and hilarity. To decline, refuse or back down from a no-balls is an extreme act of cowardice.